September 12, 1884.] 



SCIENCE. 



229 



To wing-nets. 



As to the towing-nets for collecting at the 

 surface, and at depths intermediate between 

 the surface and the bottom, we have but a single 

 noteworthy improvement to mention, — the 

 gravitating-trap of Commander Sigsbee, which 

 was successfully worked on the last dredging- 

 cruise of the steamer Blake. It is designed to 

 traverse rapidly anj T given vertical space at any 

 required depth, for the purpose of determining 

 the character and abundance of life at different 

 levels. It does not, however, afford the means 

 of obtaining continuous horizontal towings at 

 intermediate depths, unmixed with the life of 

 higher levels ; such a result being still a subject 

 for future investigation. 



The gravitating-trap (fig. 5) consists of a 

 brass cylinder, two feet long b} T forty inches in 

 diameter, riveted to a wrought-iron frame, cov- 

 ered with gauze at the upper end, and having a 

 flap-valve opening inward at the lower. It is 

 suspended to the wire dredge-rope on which it 

 travels, by means of a friction-clamp ; while at 

 the point below, to which it is to descend, there 

 is a friction-buffer. The weight of the cylin- 

 der and its frame, from the manner in which 



they are suspended, keeps the valve closed 

 until the apparatus has been lowered to the 

 highest level from which it is desired to take 

 the specimen. Every thing being in readiness, 

 a small weight or messenger is sent down the 

 rope, which, on striking the friction-clamp, dis- 

 engages it, allowing the cylinder-clamp and 

 messenger to descend by their own weight to 

 the buffer. As the cylinder strikes the buffer, 

 the valve closes, and is held in this position, 

 during the hauling-back, by the weight above it. 

 This implement may be worked at airy depth, 

 and the distance traversed by the C3 T linder may 

 be regulated at will. The many details of con- 

 struction have been purposely omitted. 



For the ordinary towing-nets for surface- 

 collecting, and for use in connection with the 

 trawl-wings, silk bolting-cloth, which can be 

 obtained of any size of mesh, has been sub- 

 stituted for the various other kinds of cloth 

 formerly employed. Bolting - cloth, though 

 moderately expensive, is very strong and dur- 

 able, and the nets constructed of it have given 

 great satisfaction. The towing-net frames are 

 made of heavy brass wire, and are generally 

 circular in shape, though an elongated rectan- 

 gular frame is sometimes employed. 



AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



THE PHILADELPHIA MEETING. 



We have made arrangements for publishing 

 reports and abstracts of so man}" of the papers 

 presented at Philadelphia, that our readers 

 can soon judge for themselves of the scientific 

 importance of the meeting ; and we shall there- 

 fore restrict our editorial comments, this week, 

 to some general impressions which were formed 

 during the progress of the session. 



The intense heat of the first five days was a 

 serious drawback from the pleasure of attend- 

 ance, but it was the only drawback. It doubt- 

 less deterred from the journey a few who would 

 otherwise have been present ; but the arrange- 

 ments of the Philadelphians were so complete, 

 that those who were in the city encountered 

 the minimum of discomfort, and enjoyed the 

 utmost benefits which a great convention can 

 afford. It was particularly fortunate that Sat- 

 urday was kept free from all sessions, for many 

 persons were thus enabled to devote two days 

 to refreshment by the seashore or in the moun- 

 tains in the company of their associates and 

 friends. Every thing which could be done 



by an enlightened and wealthy community, 

 devoted to hospitality, was done to show an 

 interest in, and respect for, the workers in 

 science, American and foreign. Nothing was 

 forgotten or neglected. The permanent offi- 

 cers of the association did their part with the 

 most satisfactory efficiency. Museums, libra- 

 ries, and collections were freely opened ; and 

 the electrical exhibition, though not complete, 

 was far enough advanced to be an attrac- 

 tive and instructive show. The convention 

 of the mining engineers, and the convention of 

 Agassiz clubs, augmented the number of at- 

 tendants upon the meetings. 



The public interest in the sessions, as usual, 

 reached its height at the delivery of the presi- 

 dential address. On this occasion, Professor 

 Young, as our readers have already discov- 

 ered, presented a masterly review of the pres- 

 ent condition of astronomical science and of 

 the problems which next invite attack. With 

 many bright flashes, his discourse was as or- 

 derly as the solar s} T stem ; and he balanced 

 this view and that with the skill of a trained 

 physicist. It is rare on such anniversaries for 



